Solid forms of menaquinols

Abstract

Disclosed are solid forms of menaquinol and processes for obtaining them by chemical or enzymatic reduction of menaquinone. Said solid forms possess high stability to oxidation which allows effective use of menaquinol in the most common formulations wherein vitamin K2 is used.

The invention claimed is: 
     
       1. A process for the preparation of a crystalline form of menaquinol of formula (II) 
       
         
           
           
               
               
           
         
         wherein n is 0 or an integer from 1 to 11, comprising the following steps:
 a) reducing menaquinone of formula (I) 
 
       
       
         
           
           
               
               
           
         
         
           wherein n is as defined above, in a biphasic system consisting of a water-immiscible solvent and an aqueous solution of sodium dithionite; 
           b) removing said solvent by evaporation to provide an aqueous phase; 
           c) Cooling and filtering the aqueous phase obtained in step b) at a temperature lower than 25° C., to give a crystalline form of menaquinol of formula (II). 
         
       
     
     
       2. The process of  claim 1  wherein step a) is performed at a temperature between 2° C. and 75° C. 
     
     
       3. The process of  claim 1  wherein the solution of sodium dithionite has a pH ranging between 3 and 8. 
     
     
       4. The process of  claim 1 , further comprising washing of the crystalline form obtained in step c) with a solution of ascorbic acid followed by drying of the crystals at a temperature not exceeding 40° C. 
     
     
       5. The process of  claim 1  wherein, in the compound of formula (II), n is 6. 
     
     
       6. The process of  claim 1  wherein, in the compound of formula (II), n is 3. 
     
     
       7. A pharmaceutical or nutraceutical composition containing the product obtained from the process of  claim 1  and a carrier.